1. Field of the Invention
The present invention relates to a method for producing an optical film, in particular, a method for producing an optical film including an antiglare layer containing light-transmitting panicles.
2. Description of the Related Art
In various image display devices such as liquid crystal display device (LCD), plasma display panel (PDP), electroluminescent display (ELD) and cathode ray tube display device (CRT), an optical film such as an antiglare and antireflection film is used on the display surface so as to prevent reduction in the contrast due to reflection of outside light or reflection of an image. The antireflection film inhibits the reflection of an image or reduces the reflection rate by scattering or interfering with light. With the recent increasingly wide-spreading usage of LCDs in an office or household environment, it is required for an optical film to enhance the antiglare property of preventing a fluorescent lamp in a room or the viewer's image from causing disturbing reflection on the display surface and further improve the display contrast in a bright place.
The optical film having an antiglare property that is inexpensive and capable of mass production includes those obtained by coating a resin containing light-transmitting particles on a surface of a transparent support to form an antiglare layer having irregularities on the surface.
JP2005-316450A discloses an optical film, wherein the layer thickness, of an antiglare layer is more than the diameter of a light-transmitting particle, the light-transmitting particles aggregate at plural points in the horizontal and vertical direction of the film, and irregularities of the antiglare layer are formed by the aggregation of the light-transmitting particles.
JP4376368B discloses an optical film, wherein the layer thickness of an antiglare layer is less than the diameter of alight-transmitting particle, and, irregularities of the antiglare layer are formed by aligning the light-transmitting particles in the antiglare layer in one step.
However, the light-transmitting particles contain coarse particles attributable to the particle production, and the coarse particles becomes a cause of point defects during the production of an antiglare film, thus leading to decrease in the production yield of the antiglare film.
In order to solve the problem, there is a method to make the particle diameter of the light-transmitting particles uniform by classifying the light-transmitting particles.